<!--伪类: 用冒号,{}-->
<!--anchor伪类:用于控制链接显示效果.用于链接,a标签-->
<!--before after伪类-->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        /*a:link{*/
            /*color: red;*/
        /*}*/
        /*a:visited{*/
            /*color: yellow;*/
        /*}*/
        /*a:hover{*/
            /*background-color: red;*/
        /*}*/
        /*a:active{*/
            /*background-color: yellow;*/
        /*}*/
        p:before{
            content: "hello1";
            color: forestgreen;
        }
        p:after{
            content: "hello2";
            color: red;
        }
    </style>
</head>
<body>
<!--<a href="https://web.sogou.com/?21997" target="_blank">点击</a>-->
<p >hello</p>
</body>
</html>